The present invention relates generally to electrical medical leads, and more particularly to stimulation leads of the type which dispense a steroid or other drug adjacent the stimulation site. The invention is particularly useful in the context of a cardiac pacing lead.
Delivery of a drug at the stimulation site of an implantable pacing lead is disclosed in U.S. Pat. No. 4,711,251, issued to Stokes. A particularly desirable configuration for such a lead is disclosed in U.S. Pat. No. 4,506,680, also issued to Stokes. In this configuration, the drug to be dispensed is compounded with silicone rubber based medical adhesive and located within a chamber within the distal end of the stimulation electrode. The drug, a steroid, acts as an anti-inflammatory agent, reducing the adverse reaction of the tissue to the stimulation electrode.
Alternative embodiments of stimulation electrodes which elute a steroid or other drugs are disclosed in U.S. Pat. No. 4,606,118 issued to Cannon et al and in U.S. Pat. No. 4,577,642 issued to Stokes. A myocardial pacing lead adapted to deliver steroid at the stimulation site is disclosed in Statutory Invention Registration No. H356, by Stokes et al, in which a steroid is delivered through a tubular electrode to a delivery point within the myocardium.
Pacing leads with extendable fixation helixes are well known to the art, such as that disclosed in U.S. Pat. No. 4,106,512, issued to Bisping and U.S. Pat. No. 4,217,913, issued to Dutcher. In Bisping, the fixation helix functions as the stimulation electrode. In Dutcher, the fixation helix serves only to affix the end of the lead to the tissue, and the lead is provided with a separate electrode located on its distal surface. In either case, the fixation helix functions to hold the distal end of the lead against the tissue to be stimulated.